(1 point) Let f(x) = 1/9 -x2. At what x-values is f' (x) zero or undefined? x = (If there is more than one such x-value, enter a comma-separated list; if there are no such x-values, enter "none".) On what interval(s) is f(x) increasing? f (x) is increasing for x in (If there is more than one such interval, separate them with "U". If there is no such interval, enter "none".) On what interval(s) is f(x) decreasing? f(x) is decreasing for x in (If there is more than one such interval, separate them with "U". If there is no such interval, enter "none".)